We want to have a survey and ask people working for IT companies if they prefer Skype to mobile phones for making calls. We want to show that in IT companies more than 20% of employees prefer to use Skype rather than a mobile phone. The null hypothesis is H0:p=0.2H0:p=0.2. State the alternative hypothesis and find out if we should use a left-tail, a right-tail or a two-tailed test to support the alternative hypothesis.

For this case we want to test if in IT companies more than 20% of employees prefer to use Skype rather than a mobile phone (alternative hypothesis) and the complement would be the the null hypothesis. So then the system of hypothesis are:

Null hypothesis:

Alternative hypothesis:

And for this case we should use a righ tail test based on the alternative hypothesis.

Step-by-step explanation:

Previous concepts

A hypothesis is defined as "a speculation or theory based on insufficient evidence that lends itself to further testing and experimentation. With further testing, a hypothesis can usually be proven true or false".  

The null hypothesis is defined as "a hypothesis that says there is no statistical significance between the two variables in the hypothesis. It is the hypothesis that the researcher is trying to disprove".  

The alternative hypothesis is "just the inverse, or opposite, of the null hypothesis. It is the hypothesis that researcher is trying to prove".  

Solution to the problem

For this case we want to test if in IT companies more than 20% of employees prefer to use Skype rather than a mobile phone (alternative hypothesis) and the complement would be the the null hypothesis. So then the system of hypothesis are:

Null hypothesis:

Alternative hypothesis:

And for this case we should use a righ tail test based on the alternative hypothesis.